Very Large Telescope findings could force physicists to rethink the Big Bang

Humans are naturally predisposed toward exceptionalism and the idea that, by some divine inherited right, we are distinct from the rest of the universe. This may actually be true if we are the only intelligent beings that exist, but even then our environment is entirely typical; from our home star to our solar system to our galaxy, we live in a spot that follows just as (quantum) mechanically from the Big Bang as any other place in the universe. As such, we should not be surprised by new and important findings from the Very Large Telescope (VLT), which blow up a long-standing hope that our galaxy is special and unique. Scans of the nearby star cluster Messier 54 have revealed distressingly — though not really surprisingly — low levels of lithium.

As stated, the problem was first identified some time ago. Dubbed the “cosmological lithium discrepancy,” the issue is very simple: everything we know about the Big Bang, supernovae, and the dynamics of stars, tells us that we should find a very specific concentration of lithium in the universe at large — but the universe actually seems to contain far less than that amount. Up until now, technological constraints made it impossible to measure the overall level of lithium in stars further out than the edges of our own galaxy; this, in turn, made it possible to maintain the rather incredible idea that perhaps the Milky Way is the only galaxy to defy our lithium predictions. Maybe the others conform perfectly to prediction — how are we to know?

The globular star cluster Messier 54, taken by the VLT Survey Telescope.

This thinking has not accurately predicted reality. The VLT was able to look into the elemental makeup of some close but still extra-galactic stars, and found that they exhibit much the same lithium deficiency found in our local stars. Though physicists could just extend their hypothetical loophole a bit further and maintain the fiction, the fact is that these stars evolved entirely separately from the Milky Way; the chances that these and only these stars just happen to share this particular, unique problem, are too low to be considered. Just 90,000 light-years away, in part of the nearby Sagittarius Dwarf Spheroidal Galaxy, these stars stand as proof that something, somewhere is wrong with our models.

The cosmic background radiation map. This is one of our primary windows back into the universe’s first moments.

Classically, so-called Big Bang nucleosynthesis is supposed to have given rise to just three basic types of elements in the instants after the creation of our universe: hydrogen, helium, and lithium. Elements heavier than lithium (element 3) usually require the focused burning of a star’s interior to form, and real heavy elements require the even more violent environment of a supernova. Modern evidence like the cosmic background radiation map can tell astronomers what the initial element-forming conditions of the Big Bang would have been like — or so we thought. While the error could very well be infinitesimally small in magnitude, and thus difficult to actually find, its effects could have compounded horribly over the universe’s billions of years of existence; in other words, this won’t be an easy error to find.

And that’s assuming there is an error, and not some totally novel outside explanation. This evidence doesn’t necessarily prove that we have wrong ideas about lithium synthesis, as the mistake could just as easily be in our understanding of the rate at which lithium is degraded after it’s formed. The lower-than-expected lithium content is actually mostly found in older stars, while younger ones occasionally have lithium levels much higher than expected. It’s a vexing problem in general, and one that will almost certainly become more profound as astronomers collect more and more information about distant galaxies.